What is Iris on Iphone?

Excuse me, could you please elaborate on what exactly Iris on iPhone refers to? Is it a new security feature, an application, or perhaps a technical term related to the camera system? I'm curious to know more about its functionality and how it might benefit users of the iPhone. Is it a recent addition, or has it been around for some time now? I'd appreciate any information you can provide to help me better understand this aspect of the iPhone.